Why do we sometimes feel like we are falling when we fall asleep?

The sensation of feeling like you are falling when you’re falling asleep is called a hypnic jerk (also known as a sleep start). It’s a common phenomenon that happens when you’re transitioning from wakefulness to sleep, usually in the early stages of the sleep cycle.

Here’s why it happens:

1. Muscle Relaxation and Brain Misinterpretation:
As your body relaxes and your muscles begin to loosen up when you drift off to sleep, your brain might misinterpret the sensation of relaxation as a signal that you’re actually falling or losing control of your body. This causes a sudden, involuntary muscle contraction—a hypnic jerk.
Essentially, your brain can confuse the muscle relaxation with the feeling of falling, leading to the sudden “jerk” or twitch you experience.
2. Evolutionary Theory:
Some researchers believe hypnic jerks could have an evolutionary basis. The theory suggests that these jerks could have evolved as a protective mechanism. In ancient times, as people relaxed into sleep, the sensation of falling could have been a warning signal to the brain to prevent them from potentially falling out of trees or from a high place during sleep.
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